PLASMA PROCESSING APPARATUS
In a plasma processing apparatus; a refrigerant flow passage being formed in the sample table and constituting an evaporator of a cooling cycle and the in-plane temperature of the sample to be processed is controlled uniformly by controlling the enthalpy of the refrigerant supplied to the refrigerant flow passage and thereby keeping the flow mode in the refrigerant flow passage, namely in the sample table, in the state of a gas-liquid two-phase. If by any chance dry out of the refrigerant occurs in the refrigerant flow passage because the heat input of plasma increases with time or by another reason, it is possible to increase speed of a compressor and inhibit the dry out from occurring in the refrigerant flow passage. Further, if the refrigerant supplied to the refrigerant flow passage is liquefied, it is kept in the gas-liquid two-phase state.
The present application claims priority from Japanese Patent Application 2008-302628 filed on Nov. 27, 2008, the content of which is hereby incorporated by reference into this application.
FIELD OF THE INVENTIONThe present invention relates to a plasma processing apparatus and a plasma processing method for applying microprocessing to a sample such as a wafer in a semiconductor production process and in particular to a temperature controller and a temperature controlling method for controlling a temperature of an electrode to retain and fix a semiconductor wafer.
BACKGROUND OF THE INVENTIONAs semiconductor devices become miniaturized, processing accuracy required for the etching of a sample increases. It is important to control the temperature of a wafer surface during etching in order to form a fine pattern on the wafer surface with a high degree of accuracy with a plasma processing apparatus. However, because of the demands for the increase of a wafer area and the improvement of an etching rate, the high-frequency power applied to a plasma processing apparatus tends to increase. In particular, in etching of a dielectric film layer, a high power in the order of kilowatts is now staring to be applied. Because of the application of a high power, the impact energy of ions on a wafer surface increases and an excessive temperature rise of a wafer is a problem during etching. Further, because of the demand for further improvement of dimensional accuracy, a means for controlling the temperature of a wafer speedy and accurately during processing is desired.
The temperature of a wafer surface in a plasma processing apparatus can be controlled by controlling the temperature of the surface of an electrostatic adsorption electrode (hereunder referred to as an electrode) touching the back surface of the wafer via a heat transfer medium. In such a conventional electrode, the temperature of the surface of the electrode has been controlled by forming a flow passage of a refrigerant in the interior of the electrode and flowing a liquid refrigerant in the flow passage. The liquid refrigerant has been supplied into the electrode flow passage after the liquid refrigerant is adjusted to a target temperature with a cooler or a heater in a refrigerant supplier. In such a refrigerant supplier, since it is configured so as to reserve a liquid refrigerant once in a liquid tank and feed the liquid refrigerant after the temperature is adjusted and the thermal capacity of the liquid refrigerant itself is large, the refrigerant supplier is effective for keeping a wafer surface to a constant temperature. However, such a refrigerant supplier is poor in temperature response, hard in high-speed temperature control, and low in heat transfer efficiency. For that reason, it has been difficult to control a wafer surface to an optimum temperature in response to the upsizing of a device accompanying the recent trend of high heat input and the progress of etching.
In view of the above situation, a direct-expansion type refrigerant supplier (hereunder referred to as a direct-expansion type cooling cycle) wherein a compressor to pressurize a refrigerant, a condenser to condense the pressurized refrigerant, and an expansion valve to expand the refrigerant are installed in an electrode of a refrigerant circulatory system and cooling is carried out by evaporating the refrigerant in a refrigerant flow passage in the electrode is proposed in JP-A No. 89864/2005 for example. In such a direct-expansion type cooling cycle, the cooling efficiency is high because the evaporative latent heat of a refrigerant is used and the evaporation temperature of the refrigerant can be controlled at a high speed by pressure. In the above method, by adopting a direct-expansion type as a refrigerant supplier for an electrode, it is possible to control the temperature of a semiconductor wafer during high heat input etching with high efficiency and at high speed.
SUMMARY OF THE INVENTIONIn a direct-expansion type cooling cycle, cooling is carried out by using latent heat obtained when a refrigerant is evaporated from a liquid into a gas and the evaporation temperature of the refrigerant can be controlled by pressure. In the case where a refrigerant is in the state of a gas-liquid two-phase in a refrigerant flow passage in an electrode, the evaporation temperature is constant as long as the pressure of the refrigerant is constant. In contrast, in the case where the phase change of a refrigerant (for example, from a liquid phase to a gas-liquid two-phase and then to a gas phase) occurs in a refrigerant flow passage, the temperature of the refrigerant cannot be kept constant in the flow passage even when the pressure of the refrigerant is kept constant. As a result, the temperature of an electrode, consequently the in-plane temperature of a sample to be processed on an electrode, cannot be controlled uniformly.
An object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can keep a refrigerant in the state of a gas-liquid two-phase in a flow passage in an electrode in order to control the in-plane temperature of a sample to be processed uniformly by using a direct-expansion type cooling cycle.
Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can control the in-plane temperature of a sample to be processed uniformly even in a direct-expansion type heating cycle.
In order to solve the above problems, a plasma processing apparatus according to the present invention has a sample table installed in a vacuum processing chamber, turns a process gas introduced into the vacuum processing chamber into a plasma gas, applies surface processing with the plasma to a sample to be processed mounted on the sample table, in which a cooling cycle having a compressor, a condenser, and an expansion valve installed outside the vacuum processing chamber is structured while a refrigerant flow passage formed in the sample table is used as an evaporator; the refrigerant flow passage has a supply port and a discharge port formed in the sample table and the cross-sectional area of the refrigerant flow passage is formed so as to increase gradually from the supply port toward the discharge port; the plasma processing apparatus includes a refrigerant evaporator controller to control the temperature and the flow rate of the refrigerant for temperature control supplied to and discharged from the refrigerant flow passage of the cooling cycle and a condensing capacity controller to control the heat exchanging capacity of the condenser; and the refrigerant for temperature control is controlled so that the refrigerant for temperature control supplied to the evaporator in the sample table may be kept in the state of a gas-liquid two-phase during the processing of the sample to be processed.
The present invention makes it possible to uniformly control the in-plane temperature of an electrode, consequently the in-plane temperature of a wafer, by adjusting the enthalpy of a refrigerant supplied into an electrode flow passage and keeping the flow mode of the refrigerant in the electrode flow passage in the state of a gas-liquid two-phase flow. More specifically, the present invention makes it possible to inhibit excessive heat exchange between the refrigerant and water for heat exchange, keep the flow mode in the state of a gas-liquid two-phase flow in the electrode flow passage, and control the in-plane temperature of a sample to be processed uniformly by controlling the condensing capacity of the refrigerant immediately before the refrigerant flows into the electrode.
Further, the present invention makes it possible to provide a temperature adjusting unit for a sample table that can uniformly control the in-plane temperature of a wafer when high heat input etching is carried out by applying a high wafer bias electric power with a direct-expansion cycle.
In a representative embodiment of the present invention, a plasma processing apparatus that turns a process gas introduced into a vacuum processing chamber into a plasma gas and applies surface processing with the plasma to a sample to be processed mounted on a sample table is characterized in that the plasma processing apparatus has a refrigerant flow passage constituting an evaporator of a cooling cycle formed in the sample table and the in-plane temperature of the sample to be processed is controlled uniformly by controlling the enthalpy of a refrigerant supplied into the refrigerant flow passage and thereby keeping the flow mode in the refrigerant flow passage, namely in the sample table, in the state of a gas-liquid two-phase flow.
Further in the present invention, a plasma processing apparatus that turns a material gas introduced into a vacuum chamber having a vacuuming means by a gas introducing means into a plasma gas and applies surface processing with the plasma to a sample to be processed is characterized in that a heating cycle having a compressor, a second heat exchanger, and an expansion valve is structured while the sample table is used as a first heat exchanger and the in-plane temperature of the sample to be processed is controlled uniformly by controlling the enthalpy of a refrigerant supplied into the refrigerant flow passage and thereby keeping the flow mode in the refrigerant flow passage, namely in the sample table, in the state of a gas-liquid two-phase flow.
Here, the temperature adjusting unit in a plasma processing apparatus proposed in the present invention can be applied not only to a plasma etching device but also to a device, such as an ashing apparatus, a sputtering apparatus, an ion implanter, a resist coater, or a plasma CVD apparatus, requiring the in-plane temperature of a wafer to be controlled uniformly at high speed.
Best modes for carrying out the present invention are hereunder explained in detail in reference to the drawings.
First EmbodimentA first embodiment wherein the present invention is applied to a plasma processing apparatus as a cooling cycle to control the temperature of a sample table is explained in reference to
The sample table 1 has a base member part (a lower electrode) 1A and a dielectric film part 1B on which a processed substrate (a wafer) W is stably mounted by electrostatic adsorption. A refrigerant flow passage 2 in which a refrigerant for temperature adjustment circulates is formed in the base material 1A. He gas 12 for heat transfer is supplied from a heat transfer gas supply system 13 into the minute gap between the sample mounting upper surface of the sample table 1 and the back surface of the wafer. A high-frequency bias power source 22 and a DC power source for electrostatic adsorption (not shown in the figure) are connected to the sample table 1.
A refrigerant supply port 3 and a refrigerant discharge port 4 are connected to the refrigerant flow passage 2 formed in the base material 1A of the sample table 1. The refrigerant flow passage 2, together with an entry side refrigerant flow passage 5A, an exit side refrigerant flow passage 5B, a compressor 7, a condenser 8, an electrode entry side expansion valve (hereunder referred to as a first expansion valve) 9, an electrode exit side expansion valve (hereunder referred to as a second expansion valve) 10, and a heater for refrigerant evaporation 11, constitutes a direct-expansion type cooling cycle. Here, the refrigerant flow passage 2 formed in the sample table 1 constitutes an evaporator in the direct-expansion type cooling cycle. That is, the sample table 1 touching the refrigerant is cooled by the latent heat (the vaporization heat) obtained when the refrigerant evaporates in the refrigerant flow passage 2 formed in the sample table 1. As the refrigerant, R410 (hydrofluorocarbon) is used for example. Further, a bypass flow passage 14 bypassing a heat exchanging refrigerant flow passage 25 and a control valve 27 are attached to the condenser 8, and a flow rate valve 16 to control the flow rate of heat exchanging water supplied to a heat exchanging cooling water flow passage 29 in the condenser 8, a temperature controlling water tank 17 to control the temperature of the heat exchanging water, and others are installed in the middle of a cooling water flow passage 28. A control valve 26 to open and close the bypass flow passage 14 is installed in the middle of the passage. Further, the refrigerant evaporating heater 11 includes an electric heater, a heat exchanger similar to the condenser 8, or the like.
The reference numeral 6 represents temperature sensors installed in the sample table at plural positions in proximity to the plane on which a sample is mounted. The reference numeral 100 represents a sample table temperature controller and controls the temperature of the wafer W to be processed on the sample mounting plane so as to come to a target temperature by receiving outputs from the temperature sensors 6 and controlling the heat exhausting capacities of the compressor 7, the first expansion valve 9, the second expansion valve 10, the refrigerant evaporating heater 11, and the condenser 8. The heat exhausting capacity of the condenser 8 is variable by controlling the bypass flow passage 14, the control valves 26 and 27, the flow rate valve 16, the temperature controlling water tank 17, and others. Here, the sample table temperature controller 100 is connected to an upper-stage controller (not shown in the figure) in the plasma processing apparatus. The upper-stage controller has a recipe selector and the plasma processing apparatus and the sample table temperature controller 100 are operated and controlled on the basis of the data of a selected recipe.
The sample table temperature controller 100 is operated by software retained in an arithmetic processor and a memory unit or an I/O means and a memory unit. An example of the functional configuration of a sample table temperature controller is shown in
The temperature of the wafer W varies in accordance with processing conditions of plasma etching and the like, namely the state of heat input from plasma to the wafer W. The state of plasma generation, consequently the state of heat input to the wafer W, is determined by the electric energy supplied from the antenna power source 21 and the bias power source 22. Further, the state of heat dissipation from the wafer W is determined by an electrostatic adsorbability, the pressure of a heat transfer gas on the back surface side of the wafer, the temperature of the sample table, and others. Furthermore, when an electric heater is installed in a dielectric film part 1B or the like of the sample table, the calorific value of the heater also has to be taken into consideration. For that purpose, the integrating temperature controller 101 carries out predetermined arithmetic processing on the basis of the processing recipes 112 of the wafer and the temperature detected with the temperature sensors 6 in order to integrally control all the related devices including the direct-expansion type cooling cycle, then the refrigerant evaporator pressure and flow rate controller 102 controls the flow rate, the pressure (the evaporation temperature), and others of the refrigerant flowing in the refrigerant flow passage 2 on the basis of the result, and thereby the temperature of the wafer is controlled so as to be kept at a target temperature. Here, although the electrostatic adsorbability, the pressure of the heat transfer gas on the back surface side of the wafer, the calorific value of the heater, and others also influence the temperature of the wafer, those factors are not the features of the present invention and hence the explanations are omitted hereunder.
In the present invention, the refrigerant flow passage 2 constituting the evaporator is configured so that the refrigerant flow rate may be controlled in order to avoid the dry out of the refrigerant in the refrigerant flow passage and the cross-sectional area of the refrigerant flow passage may gradually increase from the supply port toward the discharge port. This is explained in reference to
Here, in the adoption of the present invention, the region of the refrigerant flow passage 2 may be diversified if it is desirable that the temperature distribution of the sample table 1 is controlled more uniformly and accurately. For example, a more diversified configuration can be obtained by structuring a refrigerant flow passage 2 with a first flow passage connected to a refrigerant supply port 3 formed at a position close to the outer circumference edge of the sample table 1 and branched in both the right and left directions, a second flow passage connected to a first communication flow passage and branched in both the right and left directions, a third flow passage connected to a second communication flow passage and branched in both the right and left directions, a fourth flow passage connected to a third communication flow passage and branched in both the right and left directions, and a fifth flow passage connected to a fourth communication flow passage and branched in both the right and left directions, and connecting the fifth flow passage to a refrigerant discharge port 4 formed at a position close to the center of the sample table 1. Further, the positions of the refrigerant supply port 3 and the refrigerant discharge port 4 and the dimensional difference in the cross section of the refrigerant flow passage 2 may be reversed.
The refrigerant flows into the refrigerant flow passage 2 from the refrigerant supply port 3 in the state of gas-liquid two-phase, cools the sample table 1 with the evaporative latent heat, and flows out of the refrigerant discharge port 4 in the same state. Since the heat transfer coefficient of the refrigerant changes largely from the refrigerant supply port 3 toward the refrigerant discharge port 4, the refrigerant flow passage 2 is structured so that the cross section may increase from the first flow passage 2-1 toward the third flow passage 2-3 in order to keep the heat transfer coefficient of the refrigerant constant in the refrigerant flow passage 2. By so doing, the flow rate of the refrigerant is lowered in the region of the degree of dryness wherein the heat transfer coefficient of the refrigerant increases and thereby the heat transfer coefficient of the refrigerant is prevented from increasing.
A concrete configuration example is explained in reference to
In the present embodiment, a sample table 1 touching a refrigerant is cooled by the latent heat (vaporization heat) obtained when the refrigerant evaporates in a refrigerant flow passage 2 in the sample table 1. The refrigerant is in the state of a gas-liquid two-phase in the refrigerant flow passage 2 wherein the heat exchange (evaporation) of the refrigerant occurs. That is, when the degree of dryness is represented by X, the expression 0<x<0 is obtained and the evaporation temperature of the refrigerant is theoretically constant as long as the pressure P of the refrigerant is constant in the state. In contrast, the temperature TE of the refrigerant rises basically as the pressure P of the refrigerant increases.
Consequently, in the present invention, the refrigerant temperature TE in the refrigerant flow passage 2 is set by controlling the pressure P of the refrigerant by the degree of opening of expansion valves 9 and 10 and adjusting the refrigerant flow rate Q by the rotation speed of a compressor 7.
The characteristic of the refrigerant heat transfer coefficient α of a direct-expansion type cooling cycle is shown in
In the direct-expansion type cooling cycle, cooling is carried out by using latent heat obtained when a refrigerant evaporates from a liquid to a gas and the evaporation temperature of the refrigerant can be controlled by pressure.
The evaporation temperature TE of a refrigerant does not change even when the ratio of a liquid to a gas (the degree of dryness X) changes as long as the state of the gas-liquid two-phase is maintained and the pressure P is constant. However, when the evaporation of the refrigerant proceeds and the degree of dryness changes, the heat transfer coefficient α changes largely as shown with the thin dotted line in
In the direct-expansion type cooling cycle, during the process of changing the phase from a liquid to a gas, the heat transfer mode of the refrigerant shifts from forced-convection evaporation to dry out. The forced-convection evaporation starts from the initial stage of the evaporation of the refrigerant and thereafter the heat transfer coefficient α and the pressure loss increase in proportion to the increase of the degree of dryness X. Then when the degree of dryness X of the refrigerant reaches a constant value, dry out (disappearance of a liquid film) occurs and the heat transfer coefficient α and the pressure loss ΔP lower. Here, the pressure loss ΔP does not lower so rapidly as the heat transfer coefficient. Since the heat transfer coefficient α and the pressure loss ΔP of the refrigerant change largely in accordance with the degree of dryness X of the refrigerant in the direct-expansion type cooling cycle as stated above, the control of the temperature distribution in a wafer plane is a technological problem when the direct-expansion type cooling cycle is adopted as a cooling system for the wafer.
As stated above, in order to obtain the uniform in-plane temperature of the wafer by controlling the heat transfer coefficient α and the pressure loss ΔP in accordance with the phase change of the refrigerant, the present invention is configured so that a refrigerant flow rate may be controlled so as not to cause dry out of the refrigerant in the refrigerant flow passage 2 and the cross-sectional area of the refrigerant flow passage 2 in each region may gradually increase from the supply port 3 toward the discharge port 4 in accordance with the phase change of the refrigerant.
That is, the heat transfer coefficient α of a refrigerant is lowered by increasing the flow passage cross-sectional area and thus reducing the flow rate of the refrigerant at a position corresponding to the position where the heat transfer coefficient α of the refrigerant is large, in other words at a region close to the refrigerant discharge port 4, in the general characteristic of the case where the flow passage cross-sectional area is constant as shown in
By configuring the cross-sectional area of the refrigerant flow passage 2 formed in the base material 1A so as to gradually increase from the supply port 3 toward the discharge port 4 as stated above, it is possible to equalize the heat transfer coefficient α of the refrigerant in the refrigerant flow passage 2 and inhibit the pressure loss ΔP.
That is, by configuring the cross-sectional area of the refrigerant flow passage 2 so as to gradually increase from the supply port 3 toward the discharge port 4 in the state where the refrigerant flow rate is controlled so as not to cause dry out in the refrigerant flow passage 2, it is possible to inhibit the unevenness of the refrigerant evaporation temperature caused by the pressure loss ΔP and keep the in-plane temperature of the electrode of the sample table 1 uniform while the change of the heat transfer coefficient α caused by the phase change of the refrigerant is mitigated.
Meanwhile, by the method of adopting the structure of continuously changing the cross-sectional area of the refrigerant flow passage in accordance with the phase change of the refrigerant in the refrigerant flow passage, equalizing the refrigerant heat transfer coefficient in the flow passage, reducing the pressure loss, and uniformly controlling the in-plane temperature of a sample to be processed as shown in
In the case where the refrigerant is in the state of a liquid or a gas, cooling is caused by sensible heat and hence the temperature of the refrigerant changes in accordance with the change of the enthalpy even when the refrigerant pressure is constant. As a result, in order to uniformly control the in-plane temperature of an electrode, consequently the in-plane temperature of the wafer, with a direct-expansion type cooling cycle, it is necessary to optimize the flow passage shape (the cross-sectional area) of the electrode in consideration of the heat transfer coefficient and the pressure loss and simultaneously to configure a temperature adjusting system so that the refrigerant supplied to and discharged from the electrode may be always in the state of a gas-liquid two-phase regardless of the change of process conditions.
In a transitional case in particular, such as the case where it is necessary to rapidly set the plane of the sample table on which a sample is mounted at a desired temperature when the processing of a wafer starts by plasma etching, the case where it is necessary to keep the temperature of the plane on which a sample is mounted constant even when the heat input state to a wafer W changes largely in accordance with the change of a wafer processing recipe, or the case where it is necessary to rapidly change the temperature of the plane on which a sample is mounted to another set temperature in accordance with the change of a processing recipe, the required temperature control characteristics of the sample table must be satisfied. More specifically, it is requested to configure a temperature adjusting system as a temperature adjusting unit suitable for a sample table for microprocessing so that the refrigerant in the sample table may always be in the state of a gas-liquid two-phase even when dynamic temperature change of about 1° C./sec occurs.
The temperature adjusting system according to the present invention makes it possible to always keep the refrigerant in the refrigerant flow passage 2 formed in the sample table in the state of a gas-liquid two-phase and rapidly control the in-plane temperature of a wafer at a desired temperature even in the case where such a dynamic temperature change or a dynamic heat input state change occurs.
The configuration and operations of a temperature adjusting system according to the present invention are hereunder shown in
Firstly, the quantity of the refrigerant supplied to the electrode is increased by increasing the rotation speed of the compressor 7 at the time T1 (
When the wafer temperature is raised at a high speed with the system according to the present invention, the reverse to the control pattern shown in
The general characteristic of the cycle in the case where a heat exhausting capacity controller 103 of a condenser in a cooling cycle adopted in the present embodiment is not operated is shown in
Here, in the case where the refrigerant depressurized with the first expansion valve 9 is supplied to the refrigerant flow passage 2 in the state of a liquid as shown in
As stated above, as long as the flow mode of the refrigerant is not kept in the gas-liquid two-phase state in the refrigerant flow passage 2, the refrigerant temperature is not constant even though the refrigerant pressure is kept constant and the in-plane temperature of the electrode, consequently the in-plane temperature of a wafer, cannot be controlled uniformly.
On the other hand, a method for controlling the flow mode of the refrigerant in the case where the condenser heat exhausting capacity controller 103 is operated in the cooling cycle adopted in the first embodiment of the present invention is shown in
Successively, in the case where the refrigerant supplied to the electrode is kept in the gas-liquid two-phase state, it is necessary to control the condensing capacity and suppress excessive exhaust heat. In
In the present embodiment, it is possible to uniformly control the electrode in-plane temperature, consequently the wafer in-plane temperature, by adjusting the enthalpy of the refrigerant supplied into the electrode flow passage and keeping the flow mode of the refrigerant in the electrode flow passage in the state of the gas-liquid two-phase. More specifically, by controlling the evaporating capacity of the refrigerant immediately before the refrigerant flows into the electrode, it is possible to inhibit excessive heat exchange of heat exchanging water with the refrigerant, keep the flow mode in the state of the gas-liquid two-phase in the refrigerant flow passage, and uniformly control the in-plane temperature of a sample to be processed.
In addition, it is possible to control the in-plane temperature of a wafer rapidly and uniformly in quick response to the change of etching conditions. For example, it is possible to provide a temperature adjusting unit for a sample table capable of uniformly controlling the in-plane temperature of a wafer with a direct-expansion type cycle even though etching shifts for a short period of time from the state where a low wafer bias electric power is applied to the state of high heat input etching where a high wafer bias electric power is applied.
Second EmbodimentAs the second embodiment according to the present invention, an embodiment wherein the present invention is applied to a plasma processing apparatus as a heat pump cycle to control temperature in both heating and cooling of a sample table is explained in reference to
When a heat pump cycle is used as a cooling cycle in the second embodiment, the basic configuration and function are the same as those of the cycle adopted in the first embodiment (refer to
Meanwhile, when a heat pump cycle is used as a heating cycle, the switching of the supply/discharge ports connected to the refrigerant flow passage 2 is reversed from the case of the cooling cycle. Further, the first heat exchanger (the refrigerant flow passage formed in the sample table 1) 2 functions as a condenser and the second heat exchanger 8 (in the direct-expansion type refrigerant supply unit 60) functions as an evaporator. Consequently, a sample table temperature controller 100 has a heating/cooling operation controller 141 and a refrigerant supply/discharge direction switching control means 142 to switch the operation mode (heating cycle or cooling cycle), in addition to the functions shown in
In the case where the cross-sectional area of the refrigerant flow passage 2 in the electrode is optimized in accordance with the change of the heat transfer coefficient of the refrigerant as shown in
In contrast, in the case where the refrigerant is used in a heating cycle, the change of the heat transfer coefficient of the refrigerant in the refrigerant flow passage 2 shows a characteristic opposite to the case of the cooling cycle. That is, the heat transfer coefficient takes the maximum value at the supply port of the refrigerant and the minimum value at the discharge port of the refrigerant during condensing and heat exhausting. Consequently, in order to uniformly heat the plane of the electrode in the heating cycle, it is necessary to reverse the supply port and the discharge port of the refrigerant in the refrigerant flow passage 2 from the case of the cooling cycle.
The direction of the refrigerant supplied to the refrigerant flow passage 2 can easily be switched by installing bypass pipes 5C and 5D to bypass the parts of refrigerant flow passages 5A (5A1 and 5A2) and 5B (5B1 and 5B2) and opening/closing valves 41 to 44 as shown in
Successively, a method for controlling the flow mode of the refrigerant when heating operation is carried out with a heating cycle according to the second embodiment is shown in
In the operation of the cycle, firstly the supply of heat exchanging water to a second heat exchanger 8 is stopped, the refrigerant is depressurized and evaporated with a refrigerant evaporating heater 11 by reducing a second expansion valve 10, and the adsorbed heat is condensed with the first heat exchanger 2 of the electrode base material 1A and exhausted. Here, a bypass flow passage 14 for a condenser may be installed in place of the stoppage of the supply of the heat exchanging water to the second heat exchanger 8. When the bypass flow passage 14 is used however, the refrigerant may stagnate in the condenser 8 in the cycle and the circulation volume of the refrigerant may reduce in the cycle.
In the heating cycle too, similarly to the cooling cycle, the temperature of the refrigerant changes in accordance with the change of the enthalpy in a liquid or gaseous state and hence it is possible to uniformly raise the in-plane temperature of the electrode, consequently the in-plane temperature of a wafer, by heating the refrigerant while keeping the refrigerant flow passage 2 in the gas-liquid two-phase state.
In order to keep the refrigerant flow passage 2 constituting the first heat exchanger in the gas-liquid two-phase state in the heating cycle, it is necessary to control the enthalpy of the vapor compressed with a compressor 7 and supplied into the refrigerant flow passage 2. To this end, the enthalpy that has increased to iI is lowered to iH for example by controlling the volume and the temperature of the heat exchanging water in the second heat exchanger 8 and the refrigerant is supplied to the refrigerant flow passage 2. Further, by controlling the rotation speed of the compressor 7 and thereby securing a sufficient circulation volume of the refrigerant required for the heating capacity in the heating cycle, it is possible to discharge the refrigerant having the enthalpy iG before thoroughly liquefied as shown in the figure from the refrigerant flow passage 2, keep the refrigerant flow passage 2 in the gas-liquid two-phase state, and uniformly heat the plane of the electrode, consequently the plane of a wafer.
In the present embodiment, it is possible to uniformly control the in-plane temperature of the electrode, consequently the in-plane temperature of a wafer, by adjusting the enthalpy of the refrigerant supplied into the electrode flow passage and keeping the flow mode of the refrigerant in the gas-liquid two-phase state in the refrigerant flow passage. More specifically, by controlling the condensing capacity of the refrigerant immediately before flowing into the electrode, it is possible to inhibit the excessive heat exchange between the refrigerant and the heat exchanging water, keep the flow mode of the refrigerant in the gas-liquid two-phase state in the refrigerant flow passage, and uniformly control the in-plane temperature of a sample to be processed.
In addition, it is possible to provide a temperature adjusting unit for a sample table capable of uniformly controlling the in-plane temperature of a wafer with a direct-expansion type cycle during high heat input etching where a high wafer bias electric power is applied.
Third EmbodimentAs the third embodiment of the present invention, an example of a direct-expansion type cycle equipped with void ratio measuring devices is explained in reference to
Firstly, the flow mode of the refrigerant used in the present embodiment is shown in
The general system configuration of a plasma processing apparatus according to the third embodiment of the present invention is shown in
The temperature of a wafer W varies in accordance with the conditions of processing such as plasma etching, namely a heat input state from plasma to the wafer W and a cooling or heating state by the refrigerant in the refrigerant flow passage 2. Temperature sensors are installed in the electrode and the circulation volume and the evaporation temperature of the refrigerant during the cooling or heating cycle are controlled with a sample table temperature controller 100.
Successively, the operations in the third embodiment are explained briefly. Firstly, a wafer W is conveyed into a processing chamber 30 and mounted on and fixed to a lower electrode 1. Secondly, a process gas is supplied and the processing chamber 30 is adjusted to a prescribed processing pressure. Then plasma is generated by the electric power supply from an antenna power source 21 and a bias power source 22 and the operation of a magnetic field forming means not shown in the figure, and etching is applied with the generated plasma. The temperature of the wafer in the process is controlled by carrying out feedback control with the sample table temperature controller 100 while monitoring temperature information sent from temperature sensors 6, adjusting the heat exhausting capacities of a compressor 7, a first expansion valve 9, a second expansion valve 10, and a condenser 8, and adjusting the flow rate and the evaporation temperature of the refrigerant.
On this occasion, void ratio measuring devices 18 to measure the void ratio of the refrigerant are installed at the electrode inlet and the electrode outlet and it is monitored that the refrigerant is kept in the gas-liquid two-phase state in the refrigerant flow passage 2. The measurement result of the void ratio is reflected to the control with the sample table temperature controller 100. If by any chance dry out of the refrigerant occurs in the refrigerant flow passage 2 because the heat input of plasma increases with time or by another reason, it is possible to inhibit the dry out from occurring in the refrigerant flow passage 2 by increasing the rotation speed of the compressor 7. Further, if the refrigerant supplied to the refrigerant flow passage 2 is liquefied, it is possible to keep the refrigerant supplied to the refrigerant flow passage 2 in the gas-liquid two-phase state by the control of the flow rate valve 16 for heat exchanging water and the temperature controlling water tank 17. By so doing, the refrigerant is always kept in the gas-liquid two-phase state in the refrigerant flow passage 2 and the in-plane temperature of a sample can be controlled uniformly and rapidly.
Here, it is unnecessary to measure a void ratio quantitatively but, when you want to know the flow mode or the flow state of the refrigerant easily, a sight glass or the like may be installed at the electrode inlet or the electrode outlet. The appearance of a sight glass is shown in
By adopting such a configuration and a control method, it is possible to process the whole plane of a wafer W with a high degree of accuracy even under a high heat input etching condition wherein a high wafer bias electric power is applied.
The etching is completed through such a process and the supply of electric power, magnetic fields, and a process gas is stopped.
Here, it goes without saying that the present invention is effective even when the plasma generating method is any one of the methods such as a method for applying a high-frequency electric power other than the electric power applied to a wafer W to the electrode installed in the manner of facing the wafer W, an inductive connection method, a method of interaction between a magnetic field and a high-frequency electric power, and a method for applying a high-frequency bias electric power to the sample table 1.
Further, the present invention is also effective when deep-hole processing of a high aspect such as an aspect ratio of 15 or more is applied in accordance with processing conditions of generating a high heat input such as the case where a high-frequency bias electric power of 3 W/cm2 or more is applied to a wafer W. As a thin film for the plasma processing, a single layered film or a multilayered film including two or more kinds of films, such as a hardly workable dielectric film containing any one of SiO2, Si3N4, SiOC, SiOCH, and SiC as the main component is envisaged.
Here, it goes without saying that the similar effects can be obtained in the case of the heating cycle according to the second embodiment too by incorporating void ratio measuring devices 18 and a sight glass in the cycle in the same way as the present embodiment.
In the present embodiment, it is possible to uniformly control the electrode in-plane temperature, consequently the wafer in-plane temperature, by adjusting the enthalpy of the refrigerant supplied to the electrode flow passage and keeping the flow mode of the refrigerant in the electrode flow passage in the gas-liquid two-phase state. More specifically, by controlling the condensing capacity of the refrigerant immediately before the refrigerator flows into the electrode, it is possible to inhibit excessive heat exchange between the refrigerant and the heat exchanging water, keep the flow mode in the refrigerant flow passage in the gas-liquid two-phase state, and uniformly control the in-plane temperature of a sample to be processed.
In addition, it is possible to provide a temperature adjusting unit for a sample table capable of uniformly controlling the in-plane temperature of a wafer with a direct-expansion type cycle during high heat input etching where a high wafer bias electric power is applied.
Fourth EmbodimentThe present invention may be configured so that a refrigerant flow passage 2 may be diversified in the radial direction (from inside to outside) on the plane of a wafer. That is, as shown in
Further, in addition to the above embodiments, the present invention can also be applied to the case where a heater layer is installed in a dielectric film part. The temperature of a wafer varies in accordance with the conditions of processing such as plasma etching, namely the state of heat input from plasma to the wafer, the output power of each heater region, and the state of cooling by the refrigerant in the refrigerant flow passage 2. A temperature sensor is installed at each region of the hater layer and the electric power supplied from a heater electric source to each heater region, together with the flow rate of the refrigerant flowing in the flow passage 2 in the cooling cycle and others, is controlled with the sample table temperature controller 100.
Fifth EmbodimentThe present invention can also be applied to the case where a refrigerant flow passage formed in the sample table of a plasma processing apparatus is used as an evaporator and the cross-sectional area of the refrigerant flow passage is constant from a supply port to a discharge port. That is, it is possible to uniformly control the in-plane temperature of a sample to be processed by controlling the enthalpy of the refrigerant supplied to the refrigerant flow passage constituting an evaporator of the cooling cycle formed in a sample table of the plasma processing apparatus and thereby keeping the refrigerant flow passage, namely the flow mode in the sample table, in the gas-liquid two-phase state. Otherwise, in the case where the sample table of a plasma processing apparatus is used as a first heat exchanger and the heating cycle includes a compressor, a second heat exchanger, and an expansion valve, it is possible to uniformly control the in-plane temperature of a sample to be processed by controlling the enthalpy of the refrigerant supplied to the refrigerant flow passage and thereby keeping the flow mode in the refrigerant flow passage, namely in the sample table, in the gas-liquid two-phase state. For example, in the case of the heating cycle, in
In the present embodiment, unlike the aforementioned embodiments, there is no function of controlling the flow rate of a refrigerant and inhibiting the heat transfer coefficient of the refrigerant from increasing in the region of the degree of dryness where the heat transfer coefficient of the refrigerant increases. As a result, the drawback in the present embodiment is that the increase of the heat transfer and the pressure loss of the refrigerant cannot be inhibited in the refrigerant flow passage 2 and the in-plane temperature of a sample to be processed on a sample table is hardly controlled uniformly, but the advantage thereof is that the forming of the refrigerant flow passage in the sample table is facilitated.
Claims
1. A plasma processing apparatus that has a sample table installed in a vacuum processing chamber, turns a process gas introduced into the vacuum processing chamber into a plasma gas, and applies surface processing with the plasma to a sample to be processed mounted on the sample table,
- wherein a cooling cycle having a compressor, a condenser, and an expansion valve installed outside the vacuum processing chamber is structured while a refrigerant flow passage formed in the sample table is used as an evaporator of the cooling cycle;
- wherein the refrigerant flow passage has a supply port and a discharge port formed in the sample table and the cross-sectional area of the refrigerant flow passage is formed so as to increase gradually from the supply port toward the discharge port;
- wherein the plasma processing apparatus comprising:
- a refrigerant evaporator controller to control the temperature and the flow rate of the refrigerant for temperature control supplied to and discharged from the refrigerant flow passage of the cooling cycle; and
- a condensing capacity controller to control the heat exchanging capacity of the condenser; and
- wherein the refrigerant for temperature control is controlled so that the refrigerant for temperature control supplied to the evaporator in the sample table may be kept in the state of a gas-liquid two-phase during the processing of the sample to be processed.
2. The plasma processing apparatus according to claim 1, wherein the condensing capacity controller has a means for controlling the flow rate of a medium for heat exchange supplied to the condenser.
3. The plasma processing apparatus according to claim 1, wherein the condensing capacity controller has a means for controlling the temperature of a medium for heat exchange supplied to the condenser.
4. The plasma processing apparatus according to claim 1,
- wherein the plasma processing apparatus comprising a monitor that is installed in the heating cycle and monitors the flow mode of the refrigerant,
- wherein the refrigerant for temperature control is controlled so that the refrigerant for temperature control supplied to the evaporator in the sample table may be kept in the state of a gas-liquid two-phase on the basis of the monitoring result with the monitor during the processing of the sample to be processed.
5. A plasma processing apparatus that has a sample table installed in a vacuum processing chamber, turns a process gas introduced into the vacuum processing chamber into a plasma gas, and applies surface processing with the plasma to a sample to be processed mounted on the sample table,
- wherein a heating cycle having a compressor, a second heat exchanger, and an expansion valve installed outside the vacuum processing chamber is structured while a refrigerant flow passage formed in the sample table is used as a first heat exchanger;
- wherein the refrigerant flow passage has a supply port and a discharge port formed in the sample table and the cross-sectional area of the refrigerant flow passage is formed so as to change gradually from the supply port toward the discharge port;
- wherein the plasma processing apparatus comprising:
- a means for switching the directions of the supply and discharge of the refrigerant to and from the refrigerant flow passage formed in the sample table in order to make it possible to switch the heating cycle to both the heating and cooling cycles;
- a first heat exchanger controller to control the temperature and the flow rate of the refrigerant for temperature control supplied to and discharged from the refrigerant flow passage of the heating cycle; and
- a second heat exchanger capacity controller to control the heat exchanging capacity of the second heat exchanger,
- wherein the refrigerant for temperature control is controlled so that the refrigerant for temperature control supplied to the first heat exchanger in the sample table may be kept in the state of a gas-liquid two-phase during the processing of the sample to be processed.
6. The plasma processing apparatus according to claim 5, wherein the plasma processing apparatus has a bypass flow passage running in parallel with the second heat exchanger.
7. The plasma processing apparatus according to claim 6, wherein the second heat exchanger capacity controller has a function to control the capacity to condensate the refrigerant for temperature control flowing into the first heat exchanger.
8. The plasma processing apparatus according to claim 5, wherein the second heat exchanger capacity controller has a means for controlling the flow rate of a medium for heat exchange supplied to the second heat exchanger.
9. The plasma processing apparatus according to claim 5,
- wherein the plasma processing apparatus has a monitor that is installed in the heating cycle and monitors the flow mode of the refrigerant; and
- wherein the refrigerant for temperature control is controlled so that the refrigerant for temperature control supplied to the first heat exchanger in the sample table may be kept in the state of a gas-liquid two-phase on the basis of the monitoring result with the monitor during the processing of the sample to be processed.
10. The plasma processing apparatus according to claim 9, wherein the plasma processing apparatus has, as the monitors, void ratio measuring devices installed on both the refrigerant supply and discharge sides of the first heat exchanger in the cycle.
11. A plasma processing apparatus that has a sample table installed in a vacuum processing chamber, turns a process gas introduced into the vacuum processing chamber into a plasma gas, and applies surface processing with the plasma to a sample to be processed mounted on the sample table,
- wherein a cooling cycle having a compressor, a condenser, and an expansion valve installed outside the vacuum processing chamber is structured while a refrigerant flow passage formed in the sample table is used as an evaporator;
- wherein the plasma processing apparatus comprising:
- a refrigerant evaporator controller to control the temperature and the flow rate of the refrigerant for temperature control supplied to and discharged from the refrigerant flow passage of the cooling cycle; and
- a condensing capacity controller to control the heat exchanging capacity of the condenser,
- wherein the refrigerant for temperature control supplied to the evaporator in the sample table is kept in the state of a gas-liquid two-phase by controlling the enthalpy of the refrigerant for temperature control supplied into the refrigerant flow passage during the processing of the sample to be processed.
Type: Application
Filed: Feb 10, 2009
Publication Date: May 27, 2010
Inventors: Takumi TANDOU (Asaka), Kenetsu Yokogawa (Tsurugashima), Masaru Izawa (Hino)
Application Number: 12/368,412
International Classification: H01L 21/3065 (20060101);